CN110093054B

CN110093054B - Cross-linked copolymer, polymer electrolyte, preparation methods of cross-linked copolymer and polymer electrolyte, and all-solid-state lithium ion battery

Info

Publication number: CN110093054B
Application number: CN201810091033.XA
Authority: CN
Inventors: 高磊; 刘荣华; 单军
Original assignee: BYD Co Ltd
Current assignee: BYD Co Ltd
Priority date: 2018-01-30
Filing date: 2018-01-30
Publication date: 2021-06-18
Anticipated expiration: 2038-01-30
Also published as: CN110093054A

Abstract

The invention relates to the field of lithium ion batteries, in particular to a cross-linked copolymer, a polymer electrolyte, a preparation method of the polymer electrolyte and an all-solid-state lithium ion battery. The crosslinking type copolymer contains a crosslinked structure provided by a crosslinking agent, a structure provided by a crosslinkable copolymer, a structure provided by an ionic liquid, and a structure provided by a second polymer. The polymer electrolyte provided by the invention has higher ionic conductivity and mechanical strength, and the battery electrode attached with the polymer electrolyte membrane obtained by the method also has higher ionic conductivity and mechanical strength, so that the battery has better specific capacity, cycle life and the like.

Description

Cross-linked copolymer, polymer electrolyte, preparation methods of cross-linked copolymer and polymer electrolyte, and all-solid-state lithium ion battery

Technical Field

The invention relates to the field of lithium ion batteries, in particular to a cross-linked copolymer, a polymer electrolyte, a preparation method of the polymer electrolyte and an all-solid-state lithium ion battery.

Background

At present, liquid electrolyte is mostly used as a conductive substance in lithium ion batteries on the market, but in the use process, the liquid electrolyte is volatile, flammable and explosive, so that a plurality of safety problems can be caused, and lithium dendrites are easy to grow out, so that the application of metal lithium as a negative electrode in the batteries is limited. Therefore, solid polymer electrolytes have been proposed as an alternative. When a lithium salt is mixed with PEO, the positively charged lithium ions "dissolve" the lithium salt sufficiently in the polymer by interacting with ether oxygen functional groups in the polymer, and due to the presence of amorphous regions in the polymer, the lithium ions can be transported between polymer segments in the amorphous regions under the influence of an electric field. The solid polymer electrolyte membrane (SPE) not only plays a role in ion conduction, but also can prevent the contact of the positive electrode and the negative electrode, and can realize high safety of the lithium battery due to the characteristics of good flexibility, high-temperature stability and the like.

CN105680091A discloses a high-performance all-solid-state lithium ion battery and a preparation method thereof, wherein the high-performance all-solid-state lithium ion battery is prepared by mixing 70-90% of a high-molecular polymer and a lithium super-ion conductor: weighing high molecular polymers according to the mass ratio of 10-30%, adding the high molecular polymers into an organic solvent, adding the lithium super-ion conductor after complete dissolution, stirring, and volatilizing the solvent to form a semi-solid sol state to obtain the polymer electrolyte. In the method, the polymer electrolyte modified by the lithium super-ion conductor penetrates through the whole all-solid-state lithium ion battery system, so that the transmission rate of lithium ions is improved, and the multiplying power charging and discharging capacity of the all-solid-state lithium ion battery is improved. However, the positive and negative electrode plates need to be soaked in the polymer electrolyte to manufacture the battery, and after soaking, the gel-state polymer electrolyte is bonded with the electrode plates, so that the complexity of the lamination process and the difficulty of correct lamination are increased; in addition, the ionic conductivity of the polymer electrolyte is low, and the gap from the commercial application requirement is large.

CN105098227A discloses an all-solid-state lithium ion battery and a method for manufacturing the same, in the method, a computer program design is used, and an inkjet printing technology is used to form a positive electrode material layer, an inorganic nano filler layer, a solid electrolyte membrane layer and a negative electrode material layer of the all-solid-state lithium ion battery, so that the distribution of the inorganic nano filler presents a gradient change. Therefore, the interfacial impedance of the electrode active material/electrolyte can be reduced, the deep conduction of lithium ions is facilitated, and the capacity property of the active material is exerted to the maximum. However, this method has disadvantages in that: the particles of the anode material are large, and the ink-jet printing method is adopted, so that a conveying pipe, a spray head and the like are easily blocked, and the continuity of the manufacturing process is influenced; the positive electrode particles are easy to settle, so that the prepared positive electrode film is not uniform, and the uniformity of the battery is influenced; the conventional positive electrode slurry is viscous, so that ink-jet printing is difficult, and in order to adapt to an ink-jet process, the solid content of the slurry can be only reduced, and the battery capacity is sacrificed; the ionic conductivity of the polymer electrolyte is low, and the difference from the commercial application requirement is large.

Disclosure of Invention

The invention aims to provide a novel crosslinking copolymer and a novel polymer electrolyte with higher mechanical strength and ionic conductivity, a preparation method thereof and an all-solid-state lithium ion battery.

In order to achieve the above object, the present invention provides, in one aspect, a crosslinking-type copolymer containing a crosslinked structure provided by a crosslinking agent, a structure provided by a crosslinkable copolymer, a structure provided by an ionic liquid, and a structure provided by a second polymer; the crosslinkable copolymer contains a structural unit shown in a formula (1), a structural unit shown in a formula (2) and a structural unit shown in a formula (3), the ionic liquid is an ionic liquid with unsaturated double bonds, the tail end of the second polymer is provided with unsaturated double bonds, and the crosslinking agent is one or more of acrylate crosslinking agents containing at least two acrylate groups;

wherein R is H or C1-C4 alkyl, L is C0-C4 alkylene or-R¹-O-R²-，R¹Is C0-C4 alkylene, R²Is C0-C4 alkylene;

the acrylate group is a group represented by formula (4): -O-C (O) -C (R') ═ CH₂R' is H or C1-C4 alkyl.

In a second aspect, the present invention provides a polymer electrolyte, wherein the polymer electrolyte comprises a polymer matrix and a lithium salt dispersed in the polymer matrix, and the polymer matrix is the above cross-linked copolymer.

The third aspect of the present invention provides a method for producing a polymer electrolyte, the method comprising:

(1) providing an electrolyte slurry comprising a crosslinkable copolymer, an ionic liquid, a second polymer, a lithium salt, a crosslinking agent, and a free radical initiator;

(2) coating the electrolyte slurry on a substrate, drying to form a film, and then crosslinking and curing the obtained film;

the crosslinkable copolymer comprises a structural unit shown in a formula (1), a structural unit shown in a formula (2) and a structural unit shown in a formula (3), the ionic liquid is an ionic liquid with unsaturated double bonds, the tail end of the second polymer is provided with unsaturated double bonds, and the crosslinking agent is one or more of acrylate crosslinking agents containing at least two acrylate groups;

A fourth aspect of the present invention provides a polymer electrolyte obtained by the method of the above third aspect.

A fifth aspect of the invention provides a battery electrode or an all-solid lithium ion battery comprising the above-described polymer electrolyte.

A sixth aspect of the present invention provides a method for producing an all-solid-state lithium ion battery, including:

(A) preparing a positive electrode with a positive electrode material layer on the surface;

(B) forming an electrolyte layer on a positive electrode material layer of a positive electrode;

(C) preparing a negative electrode and disposing the negative electrode on the electrolyte layer;

the preparation of the electrolyte layer in the step (B) includes: providing electrolyte slurry containing a crosslinkable copolymer, an ionic liquid, a second polymer, a lithium salt, a crosslinking agent and a free radical initiator, coating the electrolyte slurry on a positive electrode material layer, drying to form a film, and then crosslinking and curing to form an electrolyte layer on the positive electrode material layer;

the electrolyte slurry is as hereinbefore defined.

The polymer electrolyte provided by the invention has higher ionic conductivity and mechanical strength, and the battery electrode attached with the polymer electrolyte membrane obtained by the method also has higher ionic conductivity and mechanical strength, so that the battery has better specific capacity, cycle life and the like.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The present invention provides, in one aspect, a crosslinked copolymer containing a crosslinked structure provided by a crosslinking agent, a structure provided by a crosslinkable copolymer, a structure provided by an ionic liquid, and a structure provided by a second polymer; the crosslinkable copolymer contains a structural unit shown in a formula (1), a structural unit shown in a formula (2) and a structural unit shown in a formula (3), the ionic liquid is an ionic liquid with unsaturated double bonds, the tail end of the second polymer is provided with unsaturated double bonds, and the crosslinking agent is one or more of acrylate crosslinking agents containing at least two acrylate groups;

According to the invention, the cross-linked copolymer of the invention presents a three-dimensional network structure, wherein unsaturated double bonds and some active groups present in the cross-linking agent, the cross-linkable copolymer, the ionic liquid and the second polymer can be bonded arbitrarily, including inter-and intra-molecular bonding, to form the three-dimensional network structure. In particular, the double bond of the crosslinking agent and the double bond of the structural unit represented by formula (3) of the crosslinkable copolymer, the double bond of the ionic liquid, the double bond of the second polymer initiate polymerization, and a plurality of double bonds of the one molecular crosslinking agent may be bonded to the double bonds of a plurality of structural units represented by formula (3) of the crosslinkable copolymer, or to the double bonds of a plurality of structural units represented by formula (3) of the crosslinkable copolymer, the multi-molecular ionic liquid and the multi-molecular second polymer, or the double bonds of a plurality of structural units represented by formula (3) of the crosslinkable copolymer may be bonded to the double bonds of a plurality of crosslinking agents; of course, the cross-linkable copolymer, the ionic liquid and the second polymer may all be bonded to each other and to different molecules, thereby forming a three-dimensional network of cross-linked copolymers. Such a crosslinked polymer can improve ionic conductivity and mechanical strength when used as a polymer matrix in an electrolyte layer or an electrode sheet.

In the present invention, specific examples of the alkyl group having C1 to C4 may be, for example, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group or a tert-butyl group.

Specific examples of the alkylene group having C0-C4 may be, for example, an alkylene group having C0, -CH₂-、-CH₂CH₂-、-CH₂CH₂CH₂-、-CH(CH₃)CH₂-、-CH₂CH(CH₃)-、-CH₂CH₂CH₂CH₂-and the like. Wherein said alkylene group of C0 means absent or a linking bond, i.e. the groups on both sides of the group will be directly linked.

Preferably, R is H, methyl or ethyl, L is C0 alkylene, -CH₂-、-CH₂CH₂-、-CH₂CH₂CH₂-、-O-、-O-CH₂-、-O-CH₂CH₂-、-CH₂-O-、-CH₂-O-CH₂-、-CH₂-O-CH₂CH₂-、-CH₂CH₂-O-、-CH₂CH₂-O-CH₂-or-CH₂CH₂-O-CH₂CH₂-; r' is H, methyl or ethyl.

According to the present invention, the molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2) and the structural unit represented by formula (3) in the crosslinkable copolymer may vary within a wide range, and it is preferable that the molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2) and the structural unit represented by formula (3) is 100: 0.5-25: 0.5-20, preferably 100: 1-21: 0.5-15, more preferably 100: 1-15: 1-10, more preferably 100: 1-8: 1-6. In a most preferred embodiment, the structural unit of the crosslinkable copolymer is composed of a structural unit represented by formula (1), a structural unit represented by formula (2), and a structural unit represented by formula (3). The crosslinkable copolymer is preferably a linear random copolymer composed of a structural unit represented by the formula (1), a structural unit represented by the formula (2) and a structural unit represented by the formula (3).

According to the present invention, the weight average molecular weight of the crosslinkable copolymer may vary within a relatively wide range, preferably the weight average molecular weight of the crosslinkable copolymer is 5,000-5,000,000g/mol, preferably 50,000-1,000,000g/mol, more preferably 50,000-500,000g/mol, still more preferably 50,000-95,000g/mol, for example 60,000-95,000 g/mol.

According to the invention, the cross-linking agent is one or more of acrylate cross-linking agents containing at least two acrylate groups, and the acrylate groups of the group shown in the formula (4) can be acrylate groups, methacrylate groups and the like. Preferably, the crosslinking agent is ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, tetraethylene glycol dimethacrylate, tetraethylene glycol diacrylate, 1, 3-propylene glycol dimethacrylate, 1, 2-propylene glycol dimethacrylate, 1, 3-propylene glycol diacrylate, 1, 2-propylene glycol diacrylate, 1, 4-butylene glycol dimethacrylate, 1, 3-butylene glycol dimethacrylate, 1, 4-butylene glycol diacrylate, 1, 3-butylene glycol diacrylate, pentaerythritol diacrylate, ethylene glycol diacrylate, propylene glycol diacrylate, butylene glycol diacrylate, one or more of pentaerythritol triacrylate and pentaerythritol tetraacrylate, more preferably one or more of triethylene glycol dimethacrylate, triethylene glycol diacrylate, pentaerythritol triacrylate and pentaerythritol tetraacrylate.

According to the invention, the ionic liquid may have various options, preferably the cationic moiety of the ionic liquid is one of the structures shown in the following formula:

wherein cation a is also referred to as 1-vinyl-3-ethylimidazole, cation b is also referred to as N-ethyl-4-vinylpiperidine, cation c is also referred to as ethylcarbamyltrimethylammonium methacrylate, cation d is also referred to as 4-methylstyryl-tributylphosphine, cation e is also referred to as 3-vinyl-N, N-dimethylpyrrole, cation f is also referred to as 1-propenyl-3-methylimidazole, cation g is also referred to as 1-vinyl-3-methylimidazole, and cation h is also referred to as 1-propenyl-3-ethylimidazole.

Wherein the anion of the ionic liquid can be an anion of an ionic liquid conventionally employed in the art, for example, the anion portion of the ionic liquid is selected from one of the following anions: cl^-、Br^-、I^-、Al₂Cl₇ ^-、Al₃Cl₁₀ ^-、Sb₂F₁₁ ^-、Fe₂Cl₇ ^-、Zn₂Cl₅ ^-、Zn₃Cl₇ ^-、CuCl₂ ^-、SnCl₂ ^-、NO₃ ^-、PO₄ ^3-、HSO₄ ^-、SO₄ ^2-、CF₃SO₃ ^-、R³OSO₃ ^-、CF₂CO₂ ^-、C₆H₅SO₃ ^-、PF₆ ^-、SbF₆ ^-、BF₄ ^-P-styrene sulfonate, B (R)³)₄ ^-And R³CB₁₁H₁₁ ^-Wherein R is³Selected from C1-C4 alkyl groups.

In a preferred embodiment of the invention, the ionic liquid is one or more of 1-vinyl-3-ethylimidazole bromide, 1-vinyl-3-ethylimidazole tetrafluoroborate, 1-vinyl-3-ethylimidazole iodide, 1-vinyl-3-ethylimidazole hexafluorophosphate, 1-ethyl-3-methylimidazole bromide, 1-ethyl-3-methylimidazole tetrafluoroborate, 1-ethyl-3-methylimidazole iodide, 1-ethyl-3-methylimidazole hexafluorophosphate and N-ethyl-4-vinylpiperidine bromide.

According to the present invention, the terminal of the second polymer has an unsaturated double bond, and may be one terminal or both terminals, and preferably, the structural unit in the second polymer is provided by one or more selected from the group consisting of methyl methacrylate, butyl methacrylate, isobutyl methacrylate, methyl acrylate, butyl acrylate, vinyl acetate, and styrene. For example, the second polymer may be one or more of polymethylmethacrylate, polybutylmethacrylate, polyisobutylmethacrylate, polymethyl acrylate, polybutyl acrylate, polyvinyl acetate, and polystyrene.

Wherein the molecular weight of the second polymer may vary within a wide range, preferably the weight average molecular weight of the second polymer is 5,000-500,000g/mol, preferably 10,000-100,000 g/mol.

According to the present invention, the content of each structure in the crosslinked copolymer can be varied within a wide range, and preferably, the content of the crosslinked structure in the crosslinked copolymer is 5 to 30% by weight, preferably 10 to 25% by weight, and more preferably 15 to 20% by weight; the total content of structures provided by the crosslinkable copolymer and structures provided by the second polymer is from 20 to 80% by weight, preferably from 30 to 60% by weight, more preferably from 35 to 55% by weight; the content of structures provided by the ionic liquid is 20 to 60 wt.%, preferably 30 to 50 wt.%, more preferably 35 to 48 wt.%. Preferably, the weight ratio of the structure provided by the crosslinkable copolymer and the structure provided by the second polymer is 1: 0.2 to 5, preferably 1: 0.5-2.

In a preferred embodiment of the invention, the amount of structure provided by the crosslinkable copolymer is from 10 to 40% by weight, preferably from 15 to 35% by weight, more preferably from 18 to 30% by weight; the structure provided by the second polymer is present in an amount of 10 to 40 wt%, preferably 15 to 35 wt%, more preferably 16 to 30 wt%, preferably 17 to 25 wt%.

According to the present invention, the polymer electrolyte contains the crosslinked polymer of the present invention as a polymer matrix, and a lithium salt electrolyte dispersed in the polymer matrix.

Wherein the lithium salt may be a lithium salt generally contained in a polymer electrolyte, and preferably, the lithium salt is LiClO₄、LiPF₆、LiBF₄LiBOB (lithium bis (oxalato) borate), LiN (SO)₂CF₃)₂、LiCF₃SO₃And LiN (SO)₂CF₂CF₃)₂One or more of (a).

Preferably, the lithium salt is present in an amount of 10 to 30 wt.%, preferably 15 to 27 wt.%, more preferably 18 to 22 wt.%, based on the total weight of the polymer matrix.

The selection of the groups and types of the crosslinkable copolymer, ionic liquid, second polymer and crosslinking agent described above according to the present invention is as described above and will not be described in further detail herein.

The crosslinkable copolymer according to the present invention may be prepared by a method conventional in the art, or may be a commercially available product, and the present invention is not particularly limited thereto.

The amounts of the crosslinkable copolymer, the ionic liquid, the second polymer and the crosslinking agent to be used may be selected according to the amounts of the respective structures in the crosslinkable polymer described above, and preferably, the amount of the crosslinking agent is 5 to 30% by weight, preferably 10 to 25% by weight, more preferably 15 to 20% by weight, based on the total weight of the crosslinkable copolymer, the ionic liquid, the second polymer and the crosslinking agent; the total content of the crosslinkable copolymer and the second polymer is 20 to 80% by weight, preferably 30 to 60% by weight, more preferably 35 to 55% by weight; the content of the ionic liquid is 20 to 60% by weight, preferably 30 to 50% by weight, more preferably 35 to 48% by weight. Preferably, the weight ratio of the crosslinkable copolymer to the second polymer is 1: 0.2 to 5, preferably 1: 0.5-2.

In a preferred embodiment of the present invention, the crosslinkable copolymer is present in an amount of from 10 to 40 wt.%, preferably from 15 to 35 wt.%, more preferably from 18 to 30 wt.%; the second polymer is present in an amount of 10 to 40 wt%, preferably 15 to 35 wt%, more preferably 16 to 30 wt%, preferably 17 to 25 wt%.

The selection of the lithium salt according to the invention is as described above and will not be described further here. The amount of the lithium salt may be selected as described above with respect to the content of the lithium salt in the polymer electrolyte, and preferably, the amount of the lithium salt is 10 to 30% by weight, preferably 15 to 27% by weight, and more preferably 18 to 22% by weight, based on the total weight of the crosslinkable copolymer, the ionic liquid, the second polymer, and the crosslinking agent.

According to the present invention, preferably, the radical initiator is one or more of 2-hydroxy-2-methyl propiophenone, ethyl (2,4, 6-trimethylbenzoyl) phosphonate, ethyl 4-dimethylaminobenzoate, 1-hydroxycyclohexyl phenyl ketone, benzoin dimethyl ether, methyl o-benzoylbenzoate and 4-chlorobenzophenone. The amount of the free radical initiator may vary within wide limits and is preferably from 2 to 15% by weight, preferably from 2 to 10% by weight and more preferably from 3 to 6% by weight, based on the total weight of the crosslinkable copolymer, the ionic liquid, the second polymer and the crosslinking agent.

According to the present invention, the organic solvent used in the electrolyte slurry may have various choices, and preferably, the organic solvent used in the electrolyte slurry is one or more of N, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, chloroform, dichloromethane, and acetonitrile. The amount of the organic solvent may vary within wide limits, and is preferably from 20 to 100 parts by weight, preferably from 30 to 80 parts by weight, based on 100 parts by weight of the sum of the crosslinkable copolymer, the ionic liquid, the second polymer and the crosslinking agent.

In the step (1), the crosslinkable copolymer may be dissolved in an organic solvent, and then the second polymer, the lithium salt, the crosslinking agent, the radical initiator and the ionic liquid are sequentially introduced, stirred and mixed.

According to the present invention, in the step (2), the electrolyte slurry is coated on the substrate by a coating method conventional in the art, such as knife coating, roll coating, etc. The substrate may be any of various substrates, and in the battery field, for example, a positive electrode, a negative electrode, or the like. The temperature for drying and film forming can be, for example, 40-70 ℃, and the film can be dried basically, and therefore, the time for drying and film forming can be, for example, 0.5-3 h.

Wherein, the crosslinking curing can be heating curing, but ultraviolet irradiation curing is preferred, for this purpose, in step (2), the crosslinking curing is preferably carried out under ultraviolet irradiation, and the time of the crosslinking curing is 30s-15min, preferably 2-10 min. The ultraviolet irradiation may be performed by any ultraviolet irradiation method that is conventional in the art, and the present invention is not particularly limited thereto.

According to the present invention, a polymer electrolyte membrane can be obtained by the above method, which may further comprise drying the membrane obtained by curing and crosslinking in step (2) to remove residual solvent, moisture and the like, for example, drying at 40 to 80 ℃ for 8 to 30 hours.

The polymer electrolyte obtained by the above-described method of the present invention may be the same as the polymer electrolyte described hereinabove, as long as the polymer electrolyte obtained by the above-described method is of course in this respect.

According to the present invention, the above-mentioned polymer electrolyte is usually formed as an electrolyte layer on an electrode material layer of a battery electrode, for example, on a positive electrode material layer and/or a negative electrode material layer, thereby obtaining a corresponding positive electrode or negative electrode combined with an electrolyte layer, and obtaining an all solid-state lithium ion battery.

the electrolyte slurry is as hereinbefore defined.

According to the present invention, the positive electrode may be prepared by a method conventional in the art, and preferably, the preparation of the positive electrode includes:

(a) providing positive electrode slurry containing a positive electrode active material, a lithium salt, a crosslinkable copolymer, a crosslinking agent, a radical initiator, an ionic liquid, a conductive agent and a binder;

(b) and (b) coating the electrode slurry obtained in the step (a) on a positive current collector, drying, and then performing crosslinking and curing on the positive current collector to form a positive material layer.

Wherein, the specific selection of the crosslinkable copolymer, the crosslinking agent, the free radical initiator and the ionic liquid is as described above, and the invention is not repeated herein.

Wherein the amounts of the positive electrode active material, lithium salt, crosslinkable copolymer, crosslinking agent, radical initiator, ionic liquid, conductive agent and binder may vary within a wide range, preferably, the amount of the lithium salt is 1 to 20 parts by weight, preferably 2 to 10 parts by weight, relative to 100 parts by weight of the positive electrode active material; the crosslinkable copolymer is used in an amount of 1 to 30 parts by weight, preferably 5 to 20 parts by weight, for example 5 to 15 parts by weight; the amount of the crosslinking agent is 1 to 30 parts by weight, preferably 1 to 15 parts by weight, for example 1 to 10 parts by weight; the amount of the free radical initiator is 0.1-10 parts by weight, preferably 0.5-5 parts by weight; the ionic liquid is used in an amount of 1 to 50 parts by weight, preferably 2 to 30 parts by weight, for example 5 to 20 parts by weight; the using amount of the conductive agent is 1-30 parts by weight, preferably 2-10 parts by weight; the binder is used in an amount of 1 to 30 parts by weight, preferably 2 to 10 parts by weight.

The positive electrode active material may have various choices, and may be a positive electrode active material conventionally used in the art, for example, the positive electrode active material includes, but is not limited to, lithium cobaltate (LiCoO)₂) Lithium manganate (LiMn)₂O₄) Lithium manganate, ternary material (lithium transition metal oxide) and lithium iron phosphate (LiFePO)₄) One or more of (a).

The specific types of the electric agent and the binder are not particularly limited, and are all conventional raw materials and can be selected according to requirements.

For example, the conductive agent may be selected from one or more of superconducting carbon, conductive carbon black, conductive graphite, carbon nanotubes, graphene, and carbon nanofibers.

For example, the binder may be selected from one or more of polyvinylidene fluoride (PVDF), Styrene Butadiene Rubber (SBR), and sodium carboxymethylcellulose (CMC).

According to the present invention, the dispersion solvent in the cathode slurry may have various choices, and may be, for example, one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, tetrahydrofuran, chloroform, dichloromethane, and acetonitrile. The amount of the dispersion solvent to be used may vary within a wide range, and is preferably 10 to 1000 parts by weight, preferably 20 to 800 parts by weight, more preferably 100 to 500 parts by weight, for example 200 to 400 parts by weight, relative to 100 parts by weight of the positive electrode active material.

According to the invention, in the preparation of the positive electrode, the positive electrode slurry is coated on the positive electrode current collector in the step (b), and is dried to form a semi-dry film on the current collector, and then is crosslinked and cured by ultraviolet irradiation, so that the positive electrode material layer can be formed on the current collector. The ultraviolet irradiation may be performed by any conventional ultraviolet irradiation method in the art, and the present invention is not particularly limited thereto. The time for crosslinking and curing is 30s-15min, preferably 2-10 min.

According to the present invention, the positive electrode current collector is not particularly limited, and a positive electrode current collector conventional in the art, such as a copper foil, an aluminum foil, etc., may be used, and the thickness thereof may be, for example, 1 to 100 μm.

According to the present invention, preferably, the thickness of the positive electrode material layer is 10 to 100 μm (single-sided thickness), and the positive electrode material layer may be formed on one side or both sides of the positive electrode current collector.

The positive electrode having the positive electrode material layer on the surface thereof can be produced by the above preferred method.

According to the present invention, the electrolyte slurry in step (B) is coated on the positive electrode material layer as described above, dried to form a film, and then cross-linked and cured, so that the electrolyte layer can be formed on the positive electrode material layer. The coating, drying to form a film, crosslinking and curing are as described above for the preparation of the polymer electrolyte, and the present invention is not described in detail herein.

Preferably, the thickness of the electrolyte layer is 10 to 200 μm (single-sided thickness). If the positive electrode has positive electrode material layers formed on both sides, the electrolyte layer may be formed on the positive electrode material layers on both sides.

According to the present invention, the negative electrode of the battery may be a negative electrode conventional in the art, and may be, for example, a negative electrode current collector having metal lithium attached to the surface thereof. The negative electrode collector may be, for example, a copper foil, a copper mesh, or the like.

According to the invention, the all-solid-state lithium ion battery can be obtained by welding the positive electrode and the negative electrode with the upper electrode lugs, superposing the positive electrode and the negative electrode, and placing the superposed positive electrode and the negative electrode in the aluminum plastic film for sealing and pressing.

The polymer electrolyte provided by the invention has higher ionic conductivity and mechanical strength, and the obtained positive electrode also has higher ionic conductivity and mechanical strength, so that the battery has better specific capacity, cycle life and the like.

The present invention will be described in detail below by way of examples.

In the following examples:

crosslinkable copolymer 1# is a copolymer obtained from seiko chemical company and composed of a structural unit represented by formula (1), a structural unit represented by formula (2), and a structural unit represented by formula (3) (R ═ H, L ═ CH₂-O-CH₂-) wherein the molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2) and the structural unit represented by formula (3) is 93:6:1, and the weight-average molecular weight is 95,000 g/mol.

Crosslinkable copolymer No. 2 is a copolymer available from seiko chemical company, which is a structural unit represented by formula (1), a structural unit represented by formula (2), and a structural unit represented by formula (3) (R ═ H, L ═ CH)₂-O-CH₂-) wherein the molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2) and the structural unit represented by formula (3) is 96:1:3, and the weight-average molecular weight is 80,000 g/mol.

Crosslinkable copolymer No. 3 is a copolymer available from seiko chemical company, which is a structural unit represented by formula (1), a structural unit represented by formula (2), and a structural unit represented by formula (3) (R ═ H, L ═ CH)₂-O-CH₂-) wherein the molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2) and the structural unit represented by formula (3) is 90:5:5, and the weight-average molecular weight is 70,000 g/mol.

Crosslinkable copolymer No. 4 was a copolymer available from cheng chemical company, which was a structural unit represented by formula (1), a structural unit represented by formula (2), and a structural unit represented by formula (3) (R ═ H, L ═ CH)₂-O-CH₂-) wherein the molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2) and the structural unit represented by formula (3) is 93:6:1, and the weight-average molecular weight is 50,000 g/mol.

Crosslinkable copolymer No. 5 was a copolymer available from seiko chemical company, which was a structural unit represented by formula (1), a structural unit represented by formula (2), and a structural unit represented by formula (3) (R ═ H, L ═ CH)₂-O-CH₂-) wherein the structural unit represented by the formula (1), the structural unit represented by the formula (2) and the structural unit represented by the formula (3)The molar ratio of the units was 93:6:1, and the weight average molecular weight was 200,000 g/mol.

Crosslinkable copolymer No. 6 was a copolymer available from cheng chemical company, which was a structural unit represented by formula (1), a structural unit represented by formula (2), and a structural unit represented by formula (3) (R ═ H, L ═ CH)₂-O-CH₂-) wherein the molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2) and the structural unit represented by formula (3) is 93:6:1, and the weight-average molecular weight is 40,000 g/mol.

Copolymer 7# is a copolymer available from Nikkiso Co., Ltd, and is a random copolymer composed of a structural unit represented by formula (1) and a structural unit represented by formula (2), wherein the molar ratio of the structural unit represented by formula (1) to the structural unit represented by formula (2) is 12:1, and the weight average molecular weight is 95,000 g/mol.

Polyvinylidene fluoride: product commercially available from Aladdin Industrial Co. having a weight average molecular weight of 1.5X 10⁵～5×10⁵g/mol。

Polymethyl methacrylate: a product commercially available from aladin Industrial co, having a weight average molecular weight of about 100,000 g/mol.

Polyvinyl acetate: a product commercially available from aladin Industrial co, having a weight average molecular weight of about 80,000 g/mol.

PEO: product commercially available from Aladdin Industrial Co. having a weight average molecular weight of 10⁵～5×10⁶g/mol。

Example 1

This example is for the purpose of illustrating the crosslinked copolymer, the polymer electrolyte and the all solid-state lithium ion battery of the present invention.

Preparing a battery positive plate:

(1) 50 parts by weight of a positive electrode active material LiFePO₄12.5 parts by weight of crosslinkable copolymer 1#, 6.1 parts by weight of LiN (SO)₂CF₂CF₃)₂5.2 parts by weight of pentaerythritol tetraacrylate, 1.2 parts by weight of 2-hydroxy-2-methylpropanone, 15 parts by weight of 1-vinyl-3-ethylimidazole tetrafluoroborate (available from Aladdin Industrial Co., Ltd., the same applies hereinafter), 5 parts by weight of polyvinylidene fluorideDispersing fluoroethylene and 5 parts by weight of conductive graphite in 200 parts by weight of N-methylpyrrolidone solvent to obtain positive electrode slurry;

(2) coating the positive electrode slurry on two sides of an aluminum foil (with the thickness of 20 microns), drying for 1h at 60 ℃, then irradiating for 5min by using an ultraviolet curing instrument, then continuously drying for 24h at 60 ℃, and rolling to prepare a battery positive plate, wherein the thickness of a positive electrode material layer formed by the positive electrode slurry is 50 microns (the thickness of a single side).

Forming an electrolyte layer:

(1) 15.6 parts by weight of crosslinkable copolymer 1#, 15.6 parts by weight of polymethyl methacrylate, and 15.3 parts by weight of LiN (SO)₂CF₂CF₃)₂13 parts by weight of pentaerythritol tetraacrylate, 3 parts by weight of 2-hydroxy-2-methylpropanone and 37.5 parts by weight of 1-vinyl-3-ethylimidazole tetrafluoroborate were dispersed in 25 parts by weight of N-methylpyrrolidone solvent to obtain an electrolyte slurry;

(2) coating the electrolyte slurry on a positive electrode material layer on one surface of the battery positive plate, drying at 60 ℃ for 1h, irradiating for 5min by using an ultraviolet curing instrument to form a cured film to form an electrolyte layer, continuing drying at 60 ℃ for 24h, forming the same electrolyte layer on the reverse surface of the battery positive plate by using the same method after drying, and hot-pressing at 60 ℃ to obtain the positive electrode with the electrolyte layer attached, wherein the thickness of the electrolyte layer is 50 microns (single-side thickness).

Assembling the battery:

cutting the positive electrode and the lithium-coated copper foil attached with the electrolyte layer into slices (a negative electrode, the same below) in a glove box containing high-purity Ar atmosphere, welding a tab by using a spot welding machine, laminating the positive electrode and the negative electrode, placing the laminated slices in an aluminum-plastic film for sealing, taking out, and carrying out hot pressing at 60 ℃ for 1 h; thus, battery C1 was produced.

Example 2

Preparing a battery positive plate:

(1) 60 parts by weight of LiCoO, a positive electrode active material₂10 parts by weight of crosslinkable copolymers 2#, 4.88 parts of LiN (SO)₂CF₂CF₃)₂4.16 parts by weight of pentaerythritol tetraacrylate, 0.96 parts by weight of 4-dimethylaminoethyl benzoate, 11 parts by weight of brominated N-ethyl-4-vinylpiperidine (available from aladin Industrial co., ltd., the same shall apply hereinafter), 5 parts by weight of polyvinylidene fluoride and 4 parts by weight of conductive carbon black were dispersed in 240 parts by weight of N, N-dimethylformamide solvent to obtain positive electrode slurry;

(2) coating the positive electrode slurry on two sides of an aluminum foil (with the thickness of 20 microns), drying for 1h at 60 ℃, then irradiating for 10min by using an ultraviolet curing instrument, then continuously drying for 24h at 60 ℃, and rolling to prepare a battery positive electrode plate, wherein the thickness of a positive electrode material layer formed by the positive electrode slurry is 30 microns (the thickness of a single side).

Forming an electrolyte layer:

(1) 15 parts by weight of crosslinkable copolymer 2#, 17.3 parts by weight of polyvinyl acetate, and 15.7 parts by weight of LiN (SO)₂CF₂CF₃)₂13.4 parts by weight of pentaerythritol tetraacrylate, 3.1 parts by weight of ethyl 4-dimethylaminobenzoate and 35.5 parts by weight of brominated N-ethyl-4-vinylpiperidine are dispersed in 30 parts by weight of N, N-dimethylformamide solvent to obtain electrolyte slurry;

(2) coating the electrolyte slurry on a positive electrode material layer on one surface of the battery positive plate, drying at 60 ℃ for 1h, irradiating for 10min by using an ultraviolet curing instrument to form a cured film to form an electrolyte layer, continuing drying at 60 ℃ for 24h, forming the same electrolyte layer on the reverse surface of the battery positive plate by using the same method after drying, and hot-pressing at 60 ℃ to obtain the positive electrode with the electrolyte layer attached, wherein the thickness of the electrolyte layer is 30 microns (single-side thickness).

Assembling the battery:

cutting the positive electrode and the lithium-coated copper foil attached with the electrolyte layer into slices in a glove box containing high-purity Ar atmosphere, welding a tab by using a spot welding machine, laminating the positive electrode and the negative electrode, placing the laminated sheets in an aluminum plastic film for sealing, taking out, and carrying out hot pressing for 1h at 60 ℃; thus, battery C2 was produced.

Example 3

Preparing a battery positive plate:

(1) 70 parts by weight of LiCoO, a positive electrode active material₂7.5 parts by weight of a crosslinkable copolymer 3#, 3.66 parts by weight of LiBOB, 3.12 parts by weight of pentaerythritol tetraacrylate, 0.72 parts by weight of 2-hydroxy-2-methylpropanone, 7 parts by weight of brominated 1-ethyl-3-methylimidazole (available from Aladdin Industrial co., ltd., the same shall apply hereinafter), 5 parts by weight of polyvinylidene fluoride and 3 parts by weight of conductive graphite were dispersed in 280 parts by weight of acetonitrile solvent to obtain positive electrode slurry;

(2) coating the positive electrode slurry on two sides of an aluminum foil (with the thickness of 20 microns), drying for 1h at 60 ℃, then irradiating for 6min by using an ultraviolet curing instrument, then continuously drying for 24h at 60 ℃, and rolling to prepare a battery positive plate, wherein the thickness of a positive electrode material layer formed by the positive electrode slurry is 20 microns (the thickness of a single side).

Forming an electrolyte layer:

(1) dispersing 20 parts by weight of crosslinkable copolymer 3#, 14 parts by weight of polymethyl methacrylate, 16.7 parts by weight of LiBOB, 14.2 parts by weight of pentaerythritol tetraacrylate, 3.3 parts by weight of ethyl 4-dimethylaminobenzoate and 31.8 parts by weight of brominated 1-ethyl-3-methylimidazole in 30 parts by weight of acetonitrile solvent to obtain electrolyte slurry;

(2) coating the electrolyte slurry on a positive electrode material layer on one surface of the battery positive plate, drying at 60 ℃ for 1h, irradiating for 6min by using an ultraviolet curing instrument to form a cured film to form an electrolyte layer, continuing drying at 60 ℃ for 24h, forming the same electrolyte layer on the reverse surface of the battery positive plate by using the same method after drying, and hot-pressing at 60 ℃ to obtain the positive electrode with the electrolyte layer attached, wherein the thickness of the electrolyte layer is 20 microns (single-side thickness).

Assembling the battery:

cutting the positive electrode and the lithium-coated copper foil attached with the electrolyte layer into slices in a glove box containing high-purity Ar atmosphere, welding a tab by using a spot welding machine, laminating the positive electrode and the negative electrode, placing the laminated sheets in an aluminum plastic film for sealing, taking out, and carrying out hot pressing for 1h at 60 ℃; thus, battery C3 was produced.

Example 4

The method of embodiment 1, except that:

forming an electrolyte layer: the crosslinkable copolymer No. 1 was used in an amount of 35 parts by weight, the polymethylmethacrylate was used in an amount of 35 parts by weight, and LiN (SO)₂CF₂CF₃)₂The amount of the compound is 18.8 parts by weight, the amount of pentaerythritol tetraacrylate is 16 parts by weight, the amount of 2-hydroxy-2-methylpropanone is 3.6 parts by weight, the amount of 1-vinyl-3-ethylimidazole tetrafluoroborate is 23.1 parts by weight, and the amount of the N-methylpyrrolidone solvent is 33 parts by weight;

finally, cell C4 was obtained.

Example 5

The method of embodiment 1, except that:

forming an electrolyte layer: the amount of the crosslinkable copolymer No. 1 was 10.5 parts by weight, the amount of the polymethylmethacrylate was 10.5 parts by weight, and LiN (SO)₂CF₂CF₃)₂The amount of the compound is 20 parts by weight, the amount of pentaerythritol tetraacrylate is 17 parts by weight, the amount of 2-hydroxy-2-methylpropanone is 4 parts by weight, the amount of 1-vinyl-3-ethylimidazole tetrafluoroborate is 50 parts by weight, and the amount of the N-methylpyrrolidone solvent is 27 parts by weight;

finally, cell C5 was obtained.

Examples 6 to 8

This example is for explaining the battery positive electrode, the method for producing the same, and the all-solid-state battery of the invention.

Batteries C6, C7, and C8 were prepared according to the method described in example 1, except that crosslinkable copolymers 4#, 5#, and 6# were used instead of crosslinkable copolymer 1#, respectively, in preparing the positive electrode sheet of the battery and forming the electrolyte layer.

Comparative example 1

Preparing a battery positive plate:

(1) 50 parts by weight of positive electrode material LiFePO₄20 parts by weight of PEO, 6.1 parts by weight of LiN (SO)₂CF₂CF₃)₂Dispersing 20 parts by weight of polyvinylidene fluoride and 5 parts by weight of conductive graphite in 200 parts by weight of N-methylpyrrolidone solvent to obtain positive electrode slurry;

(2) coating the positive electrode slurry on two sides of an aluminum foil (with the thickness of 20 microns), drying for 24h at 60 ℃, and rolling to prepare a battery positive plate, wherein the thickness of a positive electrode material layer formed by the positive electrode slurry is 50 microns (the thickness of a single side).

Forming an electrolyte layer:

(1) 40 parts by weight of PEO and 10 parts by weight of LiN (SO)₂CF₂CF₃)₂Dispersing in 30 parts by weight of an N-methylpyrrolidone solvent to obtain an electrolyte slurry;

(2) the electrolyte slurry was applied to one surface of the positive electrode sheet of the above-mentioned battery, dried at 60 ℃ for 24 hours, and after drying, the same electrolyte layer was formed on the reverse surface of the positive electrode sheet of the battery by the same method, and hot-pressed at 60 ℃ to obtain a positive electrode having an electrolyte layer attached thereto, the electrolyte layer having a thickness of 50 μm (one-sided thickness).

Assembling the battery:

cutting the positive electrode and the lithium-coated copper foil attached with the electrolyte layer into slices in a glove box containing high-purity Ar atmosphere, welding a tab by using a spot welding machine, laminating the positive electrode and the negative electrode, placing the laminated sheets in an aluminum plastic film for sealing, taking out, and carrying out hot pressing for 1h at 60 ℃; thus, battery DC1 was produced.

Comparative example 2

The procedure of example 1 was followed, except that in preparing the positive electrode sheet for a battery and in forming the electrolyte layer, copolymer # 7 was used instead of crosslinkable copolymer # 1, to obtain battery DC 2.

Comparative example 3

The method of example 1 was followed except that in forming the electrolyte layer, the cross-linkable copolymer # 1 was used in equal parts by weight instead of the polymethylmethacrylate; thereby producing battery DC 3.

Comparative example 4

The method of example 1, except that no ionic liquid was used in forming the electrolyte layer; thereby producing battery DC 4.

Test example 1

The peel strength and the compacted density of the positive electrode with the electrolyte layer attached thereto in the above example, and the specific capacity of the resulting battery were tested, and the results are shown in table 1, in which:

and (3) testing the peeling strength of the positive plate: the universal testing machine of WDW-0.5 of Shenzhen Junrui testing instrument Limited is adopted for testing, and the universal testing machine specifically comprises the following components: the positive electrode sheet having the electrolyte layer adhered thereto was cut into a sample having a length of 60X 20mm, the back surface thereof was adhered to a stainless steel plate A for testing by an adhesive tape, an adhesive tape having a width of 18mm was adhered to the back surface thereof, a part of the adhesive tape was exposed, the adhesive tape was adhered to a stainless steel plate B, the stainless steel plate A, B was clamped on a testing machine, and the peel strength was tested at a speed of 30mm/min under conditions of 25 ℃ and a relative humidity of less than 5% RH.

Positive electrode compaction density test: the universal testing machine of WDW-0.5 of Shenzhen Junrui testing instrument Limited is adopted for testing, and the universal testing machine specifically comprises the following components: respectively measuring the thickness of the electrode slice and the aluminum foil by using a digital display micrometer, recording the thickness as L (mum), cutting the electrode into a wafer with the diameter of 13mm, weighing the mass as m (mg); compacted density, expressed as ρ, ρ ═ m × 10^-3/(3.14×(1.3/2)²×L×10^-4)＝7.54m/L g/cm³。

Specific capacity test: the method adopts a blue battery test system (CT2001C, blue electronic corporation of Wuhan city) to carry out charge and discharge test on the battery, and comprises the following specific processes: and (3) carrying out constant-current charge-discharge mode test on the lithium ion batteries by using a charge-discharge instrument at 60 ℃, wherein the charge cut-off voltage is 4.0V, the discharge cut-off voltage is 3.0V, and the charge-discharge multiplying power is 0.5C, and the first specific capacity and the circulating 20-time specific capacity of each lithium ion battery are obtained through test.

TABLE 1

As can be seen from table 1, the positive electrode sheet with the polymer electrolyte membrane of the present invention has high peel strength and compaction density, and the battery has high specific capacity and long cycle life.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A crosslinked copolymer characterized by containing a crosslinked structure provided by a crosslinking agent, a structure provided by a crosslinkable copolymer, a structure provided by an ionic liquid, and a structure provided by a second polymer; the crosslinkable copolymer contains a structural unit shown in a formula (1), a structural unit shown in a formula (2) and a structural unit shown in a formula (3), the ionic liquid is an ionic liquid with unsaturated double bonds, the tail end of the second polymer is provided with unsaturated double bonds, and the crosslinking agent is one or more of acrylate crosslinking agents containing at least two acrylate groups;

formula (1):

formula (2):

formula (3):

wherein R is H or C1-C4 alkyl, L is C0-C4 alkylene or-R¹-O-R²-，R¹Is C0-C4 alkylene, R²Is C0-C4 alkylene; alkylene of C0 means that the linking bond, i.e. the groups on both sides of the group, will be directConnecting;

2. The crosslinked copolymer according to claim 1, wherein R is H, methyl or ethyl, L is C0 alkylene, -CH₂-、-CH₂CH₂-、-CH₂CH₂CH₂-、-O-、-O-CH₂-、-O-CH₂CH₂-、-CH₂-O-、-CH₂-O-CH₂-、-CH₂-O-CH₂CH₂-、-CH₂CH₂-O-、-CH₂CH₂-O-CH₂-or-CH₂CH₂-O-CH₂CH₂-; r' is H, methyl or ethyl.

3. The crosslinked copolymer according to claim 2, wherein the crosslinkable copolymer has a molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2) and the structural unit represented by formula (3) of 100: 0.5-25: 0.5-20.

4. The crosslinked copolymer according to claim 3, wherein the crosslinkable copolymer has a molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2) and the structural unit represented by formula (3) of 100: 1-21: 0.5-15.

5. The crosslinked copolymer according to claim 4, wherein the crosslinkable copolymer has a molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2) and the structural unit represented by formula (3) of 100: 1-15: 1-10.

6. The crosslinked copolymer according to claim 5, wherein the crosslinkable copolymer has a molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2) and the structural unit represented by formula (3) of 100: 1-8: 1-6.

7. The crosslinking-type copolymer as claimed in claim 2, wherein the crosslinkable copolymer has a weight average molecular weight of 5,000-5,000,000 g/mol.

8. The crosslinking-type copolymer as claimed in claim 7, wherein the crosslinkable copolymer has a weight average molecular weight of 50,000-1,000,000 g/mol.

9. The crosslinking-type copolymer as claimed in claim 8, wherein the crosslinkable copolymer has a weight average molecular weight of 50,000-500,000 g/mol.

10. The crosslinked copolymer of claim 9, wherein the crosslinkable copolymer has a weight average molecular weight of 50,000-95,000 g/mol.

11. The crosslinked copolymer according to any one of claims 1 to 10, wherein the crosslinking agent is ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, tetraethylene glycol dimethacrylate, tetraethylene glycol diacrylate, 1, 3-propylene glycol dimethacrylate, 1, 2-propylene glycol dimethacrylate, 1, 3-propylene glycol diacrylate, 1, 2-propylene glycol diacrylate, 1, 4-butylene glycol dimethacrylate, 1, 3-butylene glycol dimethacrylate, 1, 4-butylene glycol diacrylate, or a mixture thereof, 1, 3-butanediol diacrylate, pentaerythritol triacrylate and pentaerythritol tetraacrylate.

12. The cross-linked copolymer according to claim 11, wherein the cross-linking agent is one or more of triethylene glycol dimethacrylate, triethylene glycol diacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate.

13. A crosslinked copolymer according to any one of claims 1-10 and 12, wherein the cationic moiety of the ionic liquid is one of the structures shown by the following formulae:

the anionic part of the ionic liquid is selected from one of the following anions: cl^-、Br^-、I^-、Al₂Cl₇ ^-、Al₃Cl₁₀ ^-、Sb₂F₁₁ ^-、Fe₂Cl₇ ^-、Zn₂Cl₅ ^-、Zn₃Cl₇ ^-、CuCl₂ ^-、SnCl₂ ^-、NO₃ ^-、PO₄ ^3-、HSO₄ ^-、SO₄ ^2-、CF₃SO₃ ^-、R³OSO₃ ^-、CF₂CO₂ ^-、C₆H₅SO₃ ^-、PF₆ ^-、SbF₆ ^-、BF₄ ^-P-styrene sulfonate, B (R)³)₄ ^-And R³CB₁₁H₁₁ ^-Wherein R is³Selected from C1-C4 alkyl groups.

14. The crosslinked copolymer of any one of claims 1-10 and 12, wherein the structure in the second polymer is provided by one or more selected from the group consisting of methyl methacrylate, butyl methacrylate, isobutyl methacrylate, methyl acrylate, butyl acrylate, vinyl acetate, and styrene.

15. The crosslinked copolymer of claim 14, wherein the second polymer is selected from one or more of polymethylmethacrylate, polybutylmethacrylate, polyisobutylmethacrylate, polymethyl acrylate, polybutyl acrylate, polyvinyl acetate, and polystyrene.

16. The crosslinked copolymer of claim 14, wherein the second polymer has a weight average molecular weight of 5,000-500,000 g/mol.

17. The crosslinked copolymer of claim 16, wherein the second polymer has a weight average molecular weight of 10,000-100,000 g/mol.

18. The crosslinked copolymer according to any one of claims 1 to 10, 12 and 15 to 17, wherein the crosslinked structure is contained in an amount of 5 to 30 wt%; the total content of structure provided by the crosslinkable copolymer and structure provided by the second polymer is 20 to 80 wt%; the content of structures provided by the ionic liquid is from 20 to 60% by weight.

19. The crosslinking copolymer as claimed in claim 18, wherein the crosslinking structure is contained in the crosslinking copolymer in an amount of 10 to 25% by weight; the total content of structure provided by the crosslinkable copolymer and structure provided by the second polymer is 30-60 wt%; the content of structures provided by the ionic liquid is from 30 to 50% by weight.

20. The crosslinked copolymer of claim 18, wherein the crosslinked copolymer has a total content of structures provided by the crosslinkable copolymer and the second polymer of 35 to 55 wt%.

21. The crosslinked copolymer of claim 18, wherein the weight ratio of the structure provided by the crosslinkable copolymer and the structure provided by the second polymer is 1: 0.2-5.

22. The crosslinked copolymer of claim 21, wherein the weight ratio of the structure provided by the crosslinkable copolymer and the structure provided by the second polymer is 1: 0.5-2.

23. A polymer electrolyte comprising a polymer matrix and a lithium salt dispersed in the polymer matrix, wherein the polymer matrix is the crosslinked copolymer according to any one of claims 1 to 22.

24. The polymer electrolyte of claim 23, wherein the lithium salt is LiClO₄、LiPF₆、LiBF₄、LiBOB、LiN(SO₂CF₃)₂、LiCF₃SO₃And LiN (SO)₂CF₂CF₃)₂One or more of (a).

25. The polymer electrolyte of claim 24, wherein the lithium salt is present in an amount of 10 to 30 wt.%, based on the total weight of the polymer matrix.

26. The polymer electrolyte of claim 25, wherein the lithium salt is present in an amount of 15 to 27 wt.%, based on the total weight of the polymer matrix.

27. The polymer electrolyte of claim 26, wherein the lithium salt is present in an amount of 18 to 22 wt.%, based on the total weight of the polymer matrix.

28. A method of preparing a polymer electrolyte, the method comprising:

formula (1):

formula (2):

formula (3):

wherein R is H or C1-C4 alkyl, L is C0-C4 alkylene or-R¹-O-R²-，R¹Is C0-C4 alkylene, R²Is C0-C4 alkylene; alkylene of C0 means that the linkage, i.e. the groups on both sides of the group, will be direct;

29. The method of claim 28, wherein R is H, methyl, or ethyl, and L is C0 alkylene, -CH₂-、-CH₂CH₂-、-CH₂CH₂CH₂-、-O-、-O-CH₂-、-O-CH₂CH₂-、-CH₂-O-、-CH₂-O-CH₂-、-CH₂-O-CH₂CH₂-、-CH₂CH₂-O-、-CH₂CH₂-O-CH₂-or-CH₂CH₂-O-CH₂CH₂-; r' is H, methyl or ethyl.

30. The method according to claim 29, wherein the crosslinkable copolymer has a molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2), and the structural unit represented by formula (3) of 100: 0.5-25: 0.5-20.

31. The method according to claim 30, wherein the crosslinkable copolymer has a molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2), and the structural unit represented by formula (3) of 100: 1-21: 0.5-15.

32. The method according to claim 31, wherein the crosslinkable copolymer has a molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2), and the structural unit represented by formula (3) of 100: 1-15: 1-10.

33. The method according to claim 32, wherein the crosslinkable copolymer has a molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2), and the structural unit represented by formula (3) of 100: 1-8: 1-6.

34. The method as claimed in claim 29, wherein the crosslinkable copolymer has a weight average molecular weight of 5,000-5,000,000 g/mol.

35. The method as claimed in claim 34, wherein the crosslinkable copolymer has a weight average molecular weight of 50,000-1,000,000 g/mol.

36. The method as claimed in claim 35, wherein the crosslinkable copolymer has a weight average molecular weight of 50,000-500,000 g/mol.

37. The method as claimed in claim 36, wherein the crosslinkable copolymer has a weight average molecular weight of 50,000-95,000 g/mol.

38. The method of any one of claims 28-37, wherein the crosslinker is ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, tetraethylene glycol dimethacrylate, tetraethylene glycol diacrylate, 1, 3-propylene glycol dimethacrylate, 1, 2-propylene glycol dimethacrylate, 1, 3-propylene glycol diacrylate, 1, 2-propylene glycol diacrylate, 1, 4-butylene glycol dimethacrylate, 1, 3-butylene glycol dimethacrylate, 1, 4-butylene glycol diacrylate, 1-diacrylate, 3-butanediol ester, pentaerythritol diacrylate, pentaerythritol triacrylate and pentaerythritol tetraacrylate.

39. The method of claim 38, wherein the cross-linking agent is one or more of triethylene glycol dimethacrylate, triethylene glycol diacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate.

40. A process according to any one of claims 28 to 37 and 39, wherein the cationic moiety of the ionic liquid is one of the structures shown by the formulae:

41. The method of any of claims 28-37 and 39, wherein the structure in the second polymer is provided by one or more selected from the group consisting of methyl methacrylate, butyl methacrylate, isobutyl methacrylate, methyl acrylate, butyl acrylate, vinyl acetate, and styrene.

42. The method of claim 41, wherein the second polymer is selected from one or more of polymethylmethacrylate, polybutylmethacrylate, polyisobutylmethacrylate, polymethyl acrylate, polybutyl acrylate, polyvinyl acetate, and polystyrene.

43. The method as in claim 42, wherein the second polymer has a weight average molecular weight of 5,000-500,000 g/mol.

44. The method as in claim 43, wherein the second polymer has a weight average molecular weight of 10,000-100,000 g/mol.

45. The method of any of claims 28-37, 39, and 42-44, wherein the crosslinking agent is present in an amount of 5-30 wt%, based on the total weight of the crosslinkable copolymer, ionic liquid, second polymer, and crosslinking agent; the total content of the crosslinkable copolymer and the second polymer is 20 to 80 wt%; the content of the ionic liquid is 20-60 wt%.

46. The method of claim 45, wherein the cross-linking agent is present in an amount of 10 to 25 weight percent, based on the total weight of the cross-linkable copolymer, ionic liquid, second polymer, and cross-linking agent; the total content of the crosslinkable copolymer and the second polymer is 30 to 60% by weight; the content of the ionic liquid is 30-50 wt%.

47. The method of claim 46, wherein the cross-linkable copolymer and the second polymer are present in a total amount of 35 to 55 weight percent, based on the total weight of the cross-linkable copolymer, the ionic liquid, the second polymer, and the cross-linking agent.

48. The method of claim 45, wherein the weight ratio of the crosslinkable copolymer and the second polymer is 1: 0.2-5.

49. The method of claim 48, wherein the weight ratio of the crosslinkable copolymer and the second polymer is 1: 0.5-2.

50. The method of any one of claims 28-37, 39, 42-44, and 46-49, wherein the lithium salt is LiClO₄、LiPF₆、LiBF₄、LiBOB、LiN(SO₂CF₃)₂、LiCF₃SO₃And LiN (SO)₂CF₂CF₃)₂One or more of (a).

51. The method of claim 50, wherein the lithium salt is present in an amount of 10 to 30 wt%, based on the total weight of the crosslinkable copolymer, ionic liquid, second polymer, and crosslinking agent.

52. The method of claim 51, wherein the lithium salt is present in an amount ranging from 15 to 27 weight percent, based on the total weight of the crosslinkable copolymer, ionic liquid, second polymer, and crosslinking agent.

53. The method of claim 52, wherein said lithium salt is present in an amount of 18 to 22 weight percent, based on the total weight of said crosslinkable copolymer, ionic liquid, second polymer, and crosslinking agent.

54. The method of claim 50, wherein the free radical initiator is one or more of 2-hydroxy-2-methylpropiophenone, ethyl 2,4, 6-trimethylbenzoylphosphonate, ethyl 4-dimethylaminobenzoate, 1-hydroxycyclohexylphenylketone, benzoin dimethyl ether, methyl o-benzoylbenzoate, and 4-chlorobenzophenone.

55. The process of claim 50, wherein the free radical initiator is present in an amount of from 2 to 15 weight percent, based on the total weight of the crosslinkable copolymer, ionic liquid, second polymer, and crosslinking agent.

56. The process of claim 55 wherein the free radical initiator is present in an amount of from 2 to 10 weight percent, based on the total weight of the crosslinkable copolymer, ionic liquid, second polymer, and crosslinking agent.

57. The method of claim 56, wherein the free radical initiator is present in an amount of 3 to 6 weight percent, based on the total weight of the crosslinkable copolymer, ionic liquid, second polymer, and crosslinking agent.

58. The method of any one of claims 28-37, 39, 42-44, 46-49, and 51-57, wherein the organic solvent employed by the electrolyte slurry is one or more of N, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, chloroform, dichloromethane, and acetonitrile.

59. The method of claim 58, wherein the organic solvent is used in an amount of 20 to 100 parts by weight, relative to 100 parts by weight of the total weight of the crosslinkable copolymer, ionic liquid, second polymer, and crosslinking agent.

60. The method according to claim 59, wherein the organic solvent is used in an amount of 30 to 80 parts by weight, relative to 100 parts by weight of the total weight of the crosslinkable copolymer, ionic liquid, second polymer, and crosslinking agent.

61. The method according to any one of claims 28 to 37, 39, 42 to 44, 46 to 49, 51 to 57 and 59 to 60, wherein in the step (2), the crosslinking curing is performed under ultraviolet irradiation, and the crosslinking curing time is 30s to 15 min.

62. The method according to claim 61, wherein in the step (2), the crosslinking curing is performed under ultraviolet irradiation, and the crosslinking curing time is 2-10 min.

63. A polymer electrolyte made by the method of any one of claims 28-62.

64. A battery electrode or an all-solid-state lithium ion battery comprising the polymer electrolyte of any one of claims 23-27 and 63.

65. A preparation method of an all-solid-state lithium ion battery comprises the following steps:

the electrolyte slurry is as defined in any one of claims 28 to 62.